# Using Diagrams to Represent Addition and Subtraction

Warmup

Activity #1

Explore Addition of 2-digit Numbers with Diagrams.

• Choose two positive numbers between 1 and 99 and type in the boxes below.​
• Click.​
• If the sum in a column is above 10 click on starting from the right.​
• Click to do another problem.

Activity #2

Explore Subtraction of 2-digit numbers with Diagrams.

• Click to begin. The decomposition process starts the subtraction process.
• Click . An equal subtraction under the column for “Ones” is initiated.
• Click . The remainder after subtraction is dropped vertically below the column.
• Click . A second equal subtraction in the column under “Tens”.
• Click . The remainder after subtraction is dropped vertically below the column.
• Enter your answer in the empty boxes. If the values are correct, the applet confirms it.
• Click the reset button at the top right corner.
•  Now, use the panel  ​in the applet to change the values.
• Repeat the steps again to do more.

Activity #3

• Choose the vertical arrangement below where digits are correctly lined up.
• Click on it.
• Finish the calculation by finding the sum.

• Choose the vertical arrangement below where digits are correctly lined up.
• Click on it.
• Finish the calculation by finding the sum.

• Calculate the sum vertically. The pen tool is found under the loop icon.
• To deselect, click on a different icon.

Challenge #1

Use the given key to answer the question that follows.

What number does this diagram represent?

Challenge #2

Find the sum 10.6 + 1.7 using vertical calculation.

Challenge #3

Find the sum 123 + 0.2 using vertical calculation.

Challenge #3